/*
 cencoder.c - c source to a base64 encoding algorithm implementation

 This is part of the libb64 project, and has been placed in the public domain.
 For details, see http://sourceforge.net/projects/libb64
 */

#include "../include/cencode.h"

const int CHARS_PER_LINE = 72;

void base64_init_encodestate(base64_encodestate* state_in)
{
	state_in->step = step_A;
	state_in->result = 0;
	state_in->stepcount = 0;
}

char base64_encode_value(char value_in)
{
	static const char* encoding =
			"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	if (value_in > 63)
		return '=';
	return encoding[(int) value_in];
}

int base64_encode_block(const char* plaintext_in, int length_in,
		char* code_out, base64_encodestate* state_in)
{
	const char* plainchar = plaintext_in;
	const char* const plaintextend = plaintext_in + length_in;
	char* codechar = code_out;
	char result;
	char fragment;

	result = state_in->result;

	switch (state_in->step)
	{
	while (1)
	{
		case step_A:
		if (plainchar == plaintextend)
		{
			state_in->result = result;
			state_in->step = step_A;
			return codechar - code_out;
		}
		fragment = *plainchar++;
		result = (fragment & 0x0fc) >> 2;
		*codechar++ = base64_encode_value(result);
		result = (fragment & 0x003) << 4;
		case step_B:
		if (plainchar == plaintextend)
		{
			state_in->result = result;
			state_in->step = step_B;
			return codechar - code_out;
		}
		fragment = *plainchar++;
		result |= (fragment & 0x0f0) >> 4;
		*codechar++ = base64_encode_value(result);
		result = (fragment & 0x00f) << 2;
		case step_C:
		if (plainchar == plaintextend)
		{
			state_in->result = result;
			state_in->step = step_C;
			return codechar - code_out;
		}
		fragment = *plainchar++;
		result |= (fragment & 0x0c0) >> 6;
		*codechar++ = base64_encode_value(result);
		result = (fragment & 0x03f) >> 0;
		*codechar++ = base64_encode_value(result);

		++(state_in->stepcount);
		if (state_in->stepcount == CHARS_PER_LINE / 4)
		{
			*codechar++ = '\n';
			state_in->stepcount = 0;
		}
	}
	}
	/* control should not reach here */
	return codechar - code_out;
}

int base64_encode_blockend(char* code_out, base64_encodestate* state_in)
{
	char* codechar = code_out;

	switch (state_in->step)
	{
	case step_B:
		*codechar++ = base64_encode_value(state_in->result);
		*codechar++ = '=';
		*codechar++ = '=';
		break;
	case step_C:
		*codechar++ = base64_encode_value(state_in->result);
		*codechar++ = '=';
		break;
	case step_A:
		break;
	}
	*codechar++ = '\n';

	return codechar - code_out;
}
